However, when sand is more economical, fly ash can be limited to 300 or fewer kilograms per cubic meter 500 or. Th is article addresses some optimal ways of specifying. When mixed with lime calcium hydroxide, pozzolans combine to form cementitious compounds. A total of ten batches were produced five each for faspc and fascfrc with various silicafume and fly ash percentages as summarized in table 1. Historically, fly ash has been used in concrete at levels ranging from 15% to 25% by mass of the cementitious material component. Because it improves many desirable properties of concrete, it is introduced either as a separately batched material or as a component of blended cement. He indicated that as a result of the report, the design engineers changed the concrete pavement specification to require 25%35% type f or n fly ash or 40%50% ground granulated blastfurnace slag in all concrete for pavements, and they anticipate. Strength and hydration heat of concrete using fly ash as a. The portland cement association document, optimizing the use of fly ash in concrete, states, although the exact amount of water reduction varies widely with the nature of the fly ash and other parameters of the mix, a gross approximation is that each 10% of fly ash should allow a water reduction of at least 3%.
What is maximum content of ggbs in concrete mix design civil4m. The ignition loss of fly ash to be used shall be within certain tolerances from the value at the time of establishing or modifying the proportions of concrete. The maximum proportion of ash derived from cocombustion materials shall not be greater than 30 % by dry mass. In some states, fly ash is specified for all concrete structures. In particular, the compression strength, tensile strength, and hardness increase when the percentage of fly ash content is increased, whereas the density decreases. Typically, 15 percent to 30 percent of the portland cement is replaced with fly ash, with even higher percentages used for mass concrete placements.
Highpercentage replacement of cement with fly ash for. Replacing cement partially by ggbs and fly ash gives similar strength after 28 days. Chapter 3 fly ash in portland cement concrete fly ash. Chapter 5 fly ash in flowable fill fly ash facts for. And the concrete industry is only one of the important entities using this abundant waste material. Fly ash is a very fineparticulate material that looks and feels like talcum powder and can be a tan to gray color, depending on its source. Currently, fly ash is used in more than 50% of all ready mixed concrete placed in the united states, yet many design professionals continue to remain overly restrictive when it comes to using fly ash in concrete. When fly ash is used at about 20 percent of the total cementitious, water demand is reduced by approximately 10 percent. Is durability the most important issue in determining the limit. Dosage rates vary depending on the type of fly ash and its reactivity level. Concrete mix design with fly ash and superplasticizer. Fly ash brick fab is a building material, specifically masonry units, containing class c or class f fly ash and water.
Weighted amount of the required quantity of fly ash then added to it and mixed for 30 sec. The compressive strength of concrete was measured by 7, 28 and 60 days and the compaction factor was taken from the measurement of workability. Mix design hints for flyash concrete concrete construction. Part 1 covering use of fly ash as a pozzolana, part 2 covering use of fly ash as an admixture for concrete, and part 3 covering use of fly ash as fine aggregate for mortar and concrete. Fly ash is a byproduct from the combustion of pulverized coal, and is widely used as an ingredient in hydrauliccement concrete.
The differences in fly ash resistivity are due to variations in ash composition. Higher fly ash contents will yield higher water reductions. The compressive strength of concrete was measured by 7, 28 and 60 days and the compaction factor was taken from the. Fly ashes tend to contribute to concrete strength at a faster rate when these components are present in finer fractions of the fly ash. Pdf the maximum percentage of fly ash to replace part of original. Ash that falls to the bottom of the boilers combustion chamber commonly called a firebox is called bottom ash. The maximum percentage of fly ash to replace part of original. Dec 21, 2017 as per is 455 portland slag cement specification and as per ammendment no 4 of may 2000. Fly ash, slag, silica fume, and natural pozzolans fly ash, ground granulated blastfurnace slag, silica fume, and natural pozzolans, such as calcined shale, calcined clay or metakaolin, are materials that, when used in conjunction with portland or blended cement, contribute to the properties of the hardened concrete through hydraulic or. Nov 14, 2017 this research investigates the maximum percent of fly ash to replace part of orginal portland cement opc in producing high strength concrete.
Aci education bulletin e3 american concrete institute. Khan and ali stated the silica fume coconut fibre reinforced concrete with 2% coconut fibre and 15% silica fume content, by cement mass, has improved mechanical properties. He indicated that as a result of the report, the design engineers changed the concrete pavement specification to require 25%35% type f or n fly ash or 40%50% ground granulated blastfurnace slag in all concrete for pavements, and they anticipate requiring the same percentages for all other concrete. But if fly ash is used as a filler to replace sand in concrete production.
Oct 30, 2018 is codes shows permissible limits for adding fly ash for various types of cements. The cured concrete will ultimately reach perform at 4,000 psi or more. Maximum compressive strength was found at a fly ash replacement percentage of 35% for concrete containing class c fly ash. Optimizing the use of fly ash in concrete portland cement. Selfcompacting concrete incorporating high volumes of class. Jis a 6201 fly ash for use in concrete the silicon dioxide content of fly ash is required to be not less than 45% regardless of the type of fly ash. Is codes shows permissible limits for adding fly ash for various types of cements. It is classified as a pozzolan and with its high silica content is used by concrete producers as a component in the range of 10 to 25% of the cementitious. The fly ash sample is sieved in 45 micron sieve and the percentage of. Currently, more than 50 percent of the concrete placed in the u.
Fly ash concrete is more likely to provide satisfactory scaling performance if the watercementitious materials ratio does not exceed 0. What is the maximum amount of fly ash that can be added to concrete exposed to deicing chemicals 25 percent you are doing a concrete placement of 750 cubic yards. Many people tried replacing opc with 50% or more using fly ash it termed as high volume fly ash concrete hvfc. Heres where the importance of fly ash in concrete becomes clear. The common cements are 33,43,53 grades which are covered as per is code 269,8112,12269. Doe methods of concrete mix design concrete technology. However, beyond 72 hours of the testing, the fly ash concrete lost about 25% more weight than the no fly ash concrete.
The replacement of cement by fly ash reduces the water demand for a given slump. The use of ggbs and fly ash is more cheaper than cement and ecofriendly than conventional. Chapter 3 fly ash in portland cement concrete fly ash facts for. Uses, benefits, and drawbacks of fly ash in construction. Selfcompacting concrete incorporating high volumes of. The 7day compressive strength of concrete cylinders containing class c fly ash remains at or above 27. Structural applications of 100 percent fly ash concrete. The maximum percentage of fly ash to replace part of. This specification establishes the requirements, test methods, and the fly ash quality monitoring program faqmp for class c, class f, ultrafine uffa, and modified f mffa fly ash used in concrete products.
Liu 14 compared abrasion resistance of no fly ash concrete with a fly ash concrete having 2 5% cement replacement. Fly ash in concrete contributes to a stronger, more durable, and more chemical resistant concrete mix. However, when sand is more economical, fly ash can be limited to 300 or fewer kilograms per cubic meter 500 or fewer pounds per cubic yard. As per astm, the fineness of the fly ash is to be checked in both dry n wet sieving. What is maximum flyash content in concrete mix design civil4m. Jul 17, 2017 fly ash is a byproduct from coalfired power plants that is frequently used as an admixture in concrete to replace a portion of the portland cement. Effects of silica fume and fly ash as partial replacement of. This research investigates the maximum percent of fly ash to replace part of orginal portland cement opc in producing high strength concrete. Fly ash or flue ash, also known as pulverised fuel ash in the united kingdom, is a coal combustion product that is composed of the particulates fine particles of burned fuel that are driven out of coalfired boilers together with the flue gases. Optimum percentage replacement of cement with flyash in casting of ferrocement cubes of dimension7. What is maximum flyash content in concrete mix design. The fly ash maximum allowed is revised to 28 to 33% but commonly it must be max. Fly ash is a byproduct from coalfired power plants that is frequently used as an admixture in concrete to replace a portion of the portland cement. Dec 21, 2017 the ppc is marked as 33 grade cement there are no specification for higher grade of cement in ppc according to is code you can replace portland cement by max 35% of fly ash content.
Fly ash particles have proved their potential as good reinforcement with aluminum alloys and show the improvement of physical and mechanical properties. Mar 15, 2002 he indicated that as a result of the report, the design engineers changed the concrete pavement specification to require 25%35% type f or n fly ash or 40%50% ground granulated blastfurnace slag in all concrete for pavements, and they anticipate requiring the same percentages for all other concrete. The percentage of slag cement to use for maximum strength development is usually between 40 and 50 percent. Portland cement consists essentially of compounds of lime calcium oxide, cao mixed with silica silicon dioxide, sio2 and alumina aluminum oxide, al2o3. Limit percentage, by weight, of cementitious materials other than portland cement in concrete as follows.
The main benefit of fly ash for concrete is that it not only reduces the amount of nondurable calcium hydroxide lime, but in the process converts it into calcium silicate hydrate csh, which is the strongest and most durable portion of the. Fly ash or flue ash, also known as pulverised fuel ash in the united kingdom, is a coal. The maximum percentage of fly ash to replace part of original portland cement opc in producing high strength concrete harun mallisa a and gidion turuallo b lecturer in civil engineering. Seventyfive percent of the fly ash must have a fineness of 45 m or less, and have. T o facilitate the efficient use and disposal of fly ash, regional authorities across the globe have developed a variety of classificati on schema. Sip 1 limits on quantity of supplementary cementitious materials.
Improvement in concrete behavior with fly ash, silicafume. Over the past several decades, the use of fly ash in concrete has had a. In psc cement manufacturing, ggbs added should not be less than 25% and should not be more than 70% compressive strength of portland slag cement should not be less than 33 mpa, means psc available in 33 grade there are no specification for higher grades of psc so according to is code you can replace. The main benefit of fly ash for concrete is that it not only reduces the amount of nondurable calcium hydroxide. The fly ash sample is sieved in 45 micron sieve and the percentage of retained on the 45 micron sieve is calculated. Experimental analysis of partial replacement of cement by.
What is the highest percentage of fly ash that can be used in readymixed concrete. However, beyond 72 hours of the testing, the fly ash concrete lost about 25% more weight than the nofly ash concrete. Fly ash is commonly used in concrete in replacement ranging from 0% to 30% by weight of the total cementitious material. Therefore the use of fly ash in structural concrete may bring a substantial saving in cement consumption and over all cost of concrete production. This is also normally the optimum percentage to use in concrete to provide the lowest permeability to the ingress of aggressive solutions and greatest. Sip 1 limits on quantity of supplementary cementitious. Large quantities of fly ash and lime are available around the world at low cost and the use of high volume fly ash and lime seems to offer the best solution to rising cement demands. Examples of low and highresistivity fly ashes are shown in fig. Many researchers have found that the incorporation of industrial byproducts such as fly ash as in producing concrete can improve properties in both fresh and hardened state of concrete. Method of fly ash concrete mixing for obtaining the best result the fly ash concrete should be prepared by the following mixing method.
This, of course, assumes an adequate airvoid system is present in the concrete and that proper construction practices are adhered to. When class f fly ash is used as a replacement for cement, the 7day compressive strength remains at or above 27. For the concrete mixtures with similar fly ash content 40%, the segregation index increased with an increase in the dosage of superplasticizer that accompanied the decrease. That was until fly ash was discovered to be a useful product. Flowable fills can use non concrete grade fly ash, which may be obtained at a reduced cost. Flowable fills can use nonconcrete grade fly ash, which may be obtained at a reduced cost.
Also, atis and karahan reported that 15% fly ash content with steel fibers. Fly ash reacts with the hydrating hydraulic cement to form a cementing medium. How many percent is the maximum fly ash to replace cement. Using fly ash in concrete national precast concrete.
Effects of silica fume and fly ash as partial replacement. Introduction fly ash is a byproduct of the burning of coal in electric power generation plants. Slag cement is also compatible with pozzolans such as fly ash or silica fume. Typically, class f fly ash is used at dosages of 15 to 25 percent by mass of cementitious material, while class c fly ash is used at dosages of 15 to 40 percent. The fly ash is an industrial waste and great hazard for our environment. Fly ash, slag, silica fume, and natural pozzolans, chapter 3. Management of large volumes of fly ash is a concern for every developed nation in the world, a concern aggravated by the wide range of chemical and physical properties that fly ash exhibits. The maximum percentage of fly ash to replace part of original portland cement opc in producing high strength concrete. How many percent is the maximum fly ash to replace cement in. The 90 days strength of fly ash concrete may be more than 140% of plain concrete.
Owing to the high concentration of calcium oxide in class c fly ash, the brick is described as. The segregation index of the concrete mixtures with similar watertocementitious materials ratio 0. What is the optimum percentage replacement of cement with. Abrasion resistance of concrete with or without fly ash was similar up to 36 hours of abrasion testing. Using fly ash in concrete is environmentally beneficial because it reduces the portland cement a major contributor of co2 required in concrete. More than 75% of all concrete is made with fly ash. This standard was first published in 1966 in three parts to cater to the requirements of fly ash for three specific uses. Fly ash can be a major ingredient in a flowable fill mix. The last 50 years has seen the use of fly ash in concrete grow dramatically with close to 15 million tons used in concrete, concrete products and grouts in the u. The mean value of compressive strength for 35% type c fly ash was slightly above 41. The ppc is marked as 33 grade cement there are no specification for higher grade of cement in ppc according to is code you can replace portland cement by max 35% of fly ash content. Fly ash improves workability for pavement concrete. Typically, fly ash is added to structural concrete at 1535 percent by weight of the cement, but up to 70 percent is added for mass concrete used in. Durability of low cost high performance fly ash concrete.